In a Jena glass bowl (recommended) whisk the eggs as if making an omelet, then add the sugar and lemon juice. Place the bowl in a saucepan of water ensuring the water does not spill into the mixture, and cook, stirring vigorously and constantly with a whisk, until it has a creamy consistency.
After the first five minutes, the mixture will foam on the surface (you can see it in the second picture below), but after about 15 minutes, the cream thickens and you can see the traces left by the whisk (as you can see in the last picture in the set below).
Take the bowl out of the saucepan and add the diced butter. Stir until the butter melts, then place a plastic wrap over the entire surface of the cream (to avoid crusting) and chill the bowl! The resulting cream, or lemon curd, is extremely tasty and can be used successfully in many desserts.
After it has cooled completely, mix the lemon curd with the whipped cream. Use a spatula, not a mixer, making wide circular top to bottom moves.
Fill the base (when completely cooled) with the lemon foam and decorate with slices of red orange as you desire. Garnish with fresh mint leaves. Serve immediately!